This invention relates to a device for temporarily implanting, in an implantable duct of a human body, and in particular in a vein of a mammal including a human, a divisible and flexible stem which may be further provided with a medical apparatus or implant fixed at one end of the stem, and more particularly a blood filter of the type that is elastically expandable in the radial direction.
If such a medical apparatus includes a blood filter, its function as a blood filter is to hold back the blood clots that may form in the course of phlebitis or other vascular or cardiovascular disorders, in order to prevent their migration towards the pulmonary arteries where they could cause an embolism.
The filters generally used for this purpose have the shape of a small umbrella consisting of a plurality of flexible branches that can be radially expanded. In the rest position (retracted state) the branches extend approximately parallel to one another and occupy a reduced dimension in the radial direction, and this allows them to be positioned in a vein. Once in place inside the vein, the branches spread automatically outward and are immobilized against the wall of the vein, thereby anchoring the filter at the desired site.
Filters of this type are preferably positioned in the inferior vena cava, a little below the level of the kidneys.
The equipment that permits positioning of the filter traditionally comprises a guide rod and a mandrel which make it possible to insert a sheath into the vein to the desired depth, in such a way that the end of the sheath arrives at the site where the filter is to be positioned. When the filter is positioned in the inferior vena cava, it is known to carry out the implanting via a percutaneous access route or by "denudation" at the level of the fight internal jugular vein.
The positioning is thus carried out starting from the jugular vein, and via the superior vena cava. After the sheath is positioned, the mandrel and the guide rod are withdrawn. The filter is then introduced into the sheath by a special syringe and displaced inside the sheath, along its entire length, by the mandrel, the latter in this case having the role of a pusher. When the filter arrives at the free end of the sheath (previously positioned at the desired site in the inferior vena cava), the filter spreads open automatically and anchors in the wall of the vein. The sheath is then removed, and the filter remains permanently in position.
The main disadvantage of this technique is that the filter can be withdrawn only by performing a very delicate surgical operation. Unfortunately, the permanent positioning of the filter in the vena cava is a source of complications, in particular, the filter can trigger a thrombosis. Moreover, the patient must take anticoagulant medication for for as long as the filter is in place.
These disadvantages are all the more regrettable since, in a great many forms of treatment, the positioning of the filter in the vein is necessary only for a limited period, generally a few weeks or a few months, corresponding to the period during which there is a real risk of embolism.
For this reason a technique has recently been proposed for implanting the filter temporarily and removably, so it can be withdrawn after a certain time has elapsed.
For this, the mandrel which is used for implanting the filter is permanently integral with the latter; after the filter is implanted, the mandrel remains inserted in the vein and projects from the body via the access route used for the implanting, that is, at the level of the neck, in the region of the jugular vein, when the filter is implanted in the vena cava. Unfortunately, such a rod, which is relatively rigid, is very uncomfortable for the patient; moreover, because the mandrel projects from the skin, it constitutes a source of infection that may lead to serious complications, especially septicaemia.
Similar problems occur when, for example, certain types of stents or medical probes are to be used.
The function of a stent is to hold open a vessel for maintaining a palency of said vessel.
European Patent #EP-533,511 discloses a "Device for maintaining substantially the patency of a bodily duct section of a patient, therefrom said device is removable, comprising an outer axially elongated catheter within which a radially self-expendable mesh can be retracted, said outer catheter having a distal portion slidable in said duct section and a proximal portion extendable externally from said patient body, an internal axially elongated operating member having a distal portion to which is connected said mesh which comprises a plurality of interwoven resilient wires, said operating member being slidable within said outer catheter for connecting said mesh to outside said body and controlling therefrom the movements of the mesh." The function of the operating stem is to remotely control the position of the expandable stent member when it is implanted in the vessel.
Because such an operating stem projects from the skin when the stent apparatus is implanted, risks of infection exist. And the projecting stem is very uncomfortable for the patient.
Identical problems occur with all medical apparatus implantable in a duct of the body of a patient (human or animal), if said apparatus comprises a stem or a catheter which is implanted in the body.
In other words, it is to be understood that any flexible stem can be a source of infection and uncomfortable for the patient if said stem projects from the patient's skin.